a chemical element that has forty protons in each nucleus and that is found principally in zircon, a crystalline silicate compound, but that can be isolated as a solid metal that is used extensively in nuclear reactors because it allows neutrons to pass through without significant resistance. (symbol: Zr)

an imaginary belt in the heavens that includes the apparent paths of the sun, moon, and most planets and is divided into twelve equal signs or parts, each named for a constellation that appears within the belt as seen from the earth. [2 definitions]

a faint band of illumination along the ecliptic, often visible in the west just after sunset or in the east just before sunrise, that is thought to be caused by the reflection of sunlight from a cloud of particles around the sun.